Circuit breaker actuated by extra-high speed electrohydraulically operated piston

ABSTRACT

Discloses an extra-high speed circuit breaker in which the force for initial contact-separation is supplied by an electrohydraulic shock wave generator. A follow-up operator is triggered into operation by the electrohydraulic operator to continue contact-separation after the electrohydraulic operator has lost its initial effectiveness.

United States Patent lnventors Philip Barkan Media, Pa.;

Edward C. Schrom, Latham, NY. 873,938

Nov. 4, 1969 Nov. 30, 1971 General Electric Company Appl. No. FiledPatented Assignee CIRCUIT BREAKER ACTUATED BY EXTRA-HIGH SPEEDELECTROI-IYDRAULICALLY OPERATED PISTON 8 Claims, 3 Drawing Figs.

US. Cl 200/82 R, 200/144 B, 313/232 Int. Cl 01h 3/24, HOlh 35/38, H01h33/66 Field of Search 200/82 R,

144 B,61.01, 8l;337/401,409, 30, 326, 315; 313/232, 23l;340/15 [56]References Cited UNITED STATES PATENTS 3,141,296 7/1964 Jacobs,Jr. et a1313/232 X 3,190,990 6/1965 Perry 200/82 X 3,334,348 8/1967 Alfano, Jr..200/82 X 3,377,511 4/1968 Richtr et a1. 200/82 X 3,486,062 12/1969Schrom 313/231 X FOREIGN PATENTS 1,118,868 12/1961 Germany ZOO/61.011,287,677 1/1969 Germany 200/82 Primary Examiner-Robert K. SchaeferAssistant Examiner-Robert A. Vanderhye Attorneys-J. Wesley Haubner,William Fredman, Frank L.

Neuhauser, Oscar B. Waddell and Joseph B. Forman ABSTRACT: Discloses anextra-high speed circuit breaker in which the force for initialcontact-separation is supplied by an electrohydraulic shock wavegenerator. A follow-up operator is triggered into operation by theelectrohydraulic operator to continue contact-separationafter theelectrohydraulic operator has lost its initial effectiveness.

CIRCUIT BREAKER ACTUATED BY EXTRA-HIGH SPEED ELECTROI-IYDRAULICALLYOPERATED PISTON This invention relates to an electric circuit breakerthat opens at extra-high speeds and relates more particularly to acircuit breaker in which the force for initial contact-separation issupplied by an electrohydraulic shock wave generator.

In certain circuit breaker applications, it is important that thecircuit breaker be opened at extreme high speeds. For example, in thealternating current circuit breaker disclosed in application Ser. No.806,19l-Kotos, filed Mar. 1 1, I969, and assigned to the assignee of thepresent invention, it is required that the opening operation beinitiated and substantially completed after the instant of peak currentand during the short period of a few milliseconds immediately precedinga natural current zero. The shorter the period in which such an openingoperation can be completed, the more its initiation can be delayed afterpassage through peak current and, accordingly, the less severe will bethe interrupting duty on the circuit breaker.

Accordingly, an object of our invention is to provide an extra-highspeed circuit breaker operator which can separate the contacts of thecircuit breaker by an effective distance of one-half inch within 1 or 2milliseconds following delivery of a tripping signal to the operator.

In attaining this object, we use an operator that relies upon theprinciple of electrohydraulics for generating a shock wave that suppliesthe energy for initiating the opening operation. As pointed out inapplication Ser. No. 814,478-Schrom, filed Jan. 13, 1969 now US. Pat.No. 3,486,062, issued Dec. 23, 1969, and assigned to the assignee of thepresent invention, an electrohydraulic shock wave generator derives itsenergy from an electric are initiated under liquid and into which alarge amount of electrical energy is rapidly discharged. A shock wave orstep pressure gradient is transmitted from the are through the-liquidand is appropriately focused onto the object being worked upon. Incarrying out our invention, we focus this shock wave onto a pistoncoupled to the movable contact of the circuit breaker, and the pistonresponds to receipt of the shock wave by rapidly moving the contactthrough the initial portion of an opening stroke.

The force pulse derived from such an electrohydraulic operator, thoughrising very rapidly to a very-high peak value, is of relatively shortduration and quickly loses its effectiveness after passing through itspeak. Another object of our invention is to provide an operatingmechanism which can continue the rapid contact separation begun by theelectrohydraulic operator immediately after this force pulse loses itseffectiveness.

In further carrying out the invention in one form, we provide a followupoperator for continuing separation of said contacts after the shock wavefrom said electrohydraulic operator has begun contact-separating motionof said piston. Restraining means prevents the followup operator fromoperating prior to operation of the electrohydraulic operator. Releasingmeans responsive to operation of the electrohydraulic operator isprovided for releasing the restraining means to cause said followupoperator to continue separation of said contacts after saidelectrohydraulic operator has lost its initial effectiveness.

For a better understanding of the invention, reference may be had to thefollowing description taken in conjunction with the accompanyingdrawings, wherein:

FIG. I is a schematic view of a circuit breaker embodying one form ofthe invention. In FIG. I the circuit breaker is shown in closedposition.

FIG. 2 shows a portion of the circuit breaker of FIG. 1 near the end ofan opening operation but prior to a resetting operation.

FIG. 3 shows the components of FIG. 2 in a position occupied when thecircuit breaker is fully open and the components reset.

INTERRUPTER Referring now to FIG. I, there is shown a high-voltage powerline 9 in which an electric circuit interrupter 10 is connected forcontrolling the current therethrough. The illustrated interrupter I0 isa conventional vacuum-type circuit interrupter that comprises a highlyevacuated housing ll. Housing I1 comprises a tubular casing ofinsulating material and a pair of metal end caps 12 and 13 sealed to thecasing at its opposite ends. Located within evacuated housing 11 are twoseparable contacts 15 and 16. Contact 16 is a stationary contact that issupported on the lower end of a conductive stationary rod 18 projectingthrough the upper end cap 12. Contact I5 is a movable contact supportedon the upper end of a movable contact rod 20 that projects through thelower end cap of housing 11. A suitable flexible metallic bellows 21forms a seal around movable contact rod 20 and allows reciprocationthereof without permitting air leakage into housing 11.

The portion of power line 9 on one side of the interrupter is suitablyconnected to the movable contact rod 20, and the portion on the oppositeside is suitably connected to stationary contact rod 18. Thus, thecircuit through the interrupter extends through conductive parts I8, l6,l5 and 20. When movable contact rod 20 is driven downwardly from itsposition of FIG. I, it separates the movable contact 15 from stationarycontact 16 to draw an arc therebetween. When the arcing current passesthrough zero, the arc is prevented from reigniting by thehigh-dielectric strength of the vacuum, thus completing the interruptingoperation. A significant characteristic of a vacuum interrupter is itsability to complete an interrupting operation with only a very smallcontact separation, e.g., onehalf to three-fourth inches.

ELECTROI-IYDRAULIC OPERATOR For separating the contacts at extreme-highspeeds, we provide an electrohydraulic operator 25. The operator 25, inmany respects, is similar to the hydraulic shock wave generatingapparatus shown and claimed in the aforesaid application Ser. No.814,478-Schrom. As such, it comprises a chamber 26 that is filled with asuitable liquid, such as water with insoluble electrically conductiveparticles suspended therein. Such a fluid system is disclosed andclaimed in US. Pat. No. 3,225,252-Schrom et al., assigned to theassignee of the present invention. At the right-hand end of theillustrated chamber is a cylindrical bore 27 in which a piston 28 isslidably mounted. In the illustrated embodiment, the internal surfacesof chamber 26 are constituted by a director surface 30 of generallyhemispherical form at the left-hand side of the chamber and a collimatorsurface 32 of frustoconical form disposed between the hemisphericalsurface and the bore and converging toward the bore.

In the center of the hemispherical surface is an opening into whichsuitable electrode structure 35 extends. This electrode structure ispreferably of the type shown and claimed in U.S. Pat. No.3.354,344-Schrom, assigned to the assignee of the present invention. Assuch, it comprises an outer electrode 36 and an inner electrode 38concentric therewith and electrical insulation 39 disposed between thetwo electrodes. The electrodes have exposed metal tips that are disposedsubstantially flush with the hemispherical surface 30.

When a sufficiently high-voltage is applied between these electrodes 36and 38, an electric arc is initiated between the exposed metal tips ofthe electrodes Through this arc a sharply rising pulse of current havinga duration of about 10 microseconds is caused to flow in a manner soonto be described. The arc reacts with the liquid in the chamber 26,vaporizing a portion of the liquid and generating a shock wave which israpidly propagated through the liquid into sharp impact with the exposedleft-hand surface of piston 28. This impact drives piston 28 atextreme-high speed toward the right, thereby extremely rapidlyseparating contact 15 from contact 16, as will soon be described.

The hemispherical surface 30 directs the shock wave into the liquid andthe conical surface 32 concentrates the energy of the shock wave into apath leading toward the piston 28. The shape of these surfaces can bevaried to change the shape and distribution of the force pulse outputfrom the electrohydraulic operator. But in a preferred form of theinvention, we use a director surface that is a divergent surface ofrevolution having its axis of revolution substantially coincident withthe electrode region in which the arc is initiated.

For terminating motion of the piston 28 without excessive shock,dashpotting action is provided by means of an annular shoulder 40 on thebore 27 coacting with an enlarged portion 28a of the piston rod. Whenthe piston 28 moves to the right, it forces liquid ahead of it into anoverflow chamber 4]. Initially this liquid flows freely into theoverflow chamber 41, but when the enlarged portion 28a enters the regionof the annular shoulder 40, a restricted flow passage is present aroundthe enlarged portion, and the impedance of this restricted passageimposes a high-decelerating force on piston 28.

A suitable piston reset spring 43 biases the piston 28 to the left andreturns it to its illustrated position of FIG. 1 after the piston hasmoved through its above-described working stroke. Any gases then presentin the liquid to the left of the piston are vented through a restrictedbleed passage 45. This bleed passage is sufficiently restricted that itdoes not significantly interfere with pressure build up in chamber 26during a normal working operation of the electrohydraulic operator 25.

IN ITIATING OPERATION OF THE ELECTROI-IYDRAULIC OPERATOR For initiatingthe aforementioned are between electrodes 36 and 38 of theelectrohydraulic operator, we provide the series combination of ahigh-voltage capacitor 50 and a normally open, turn-on switch 52connected across the electrodes. The capacitor 50 is charged from asuitable separate source (not shown) via conductors 51. When switch 52is open, insufficient voltage is present between the electrodes 36 and38 to initiate an arc therebetween. But when the switch 52 is closed,the full capacitor voltage is available across the electrodes, thusproducing the desired arc-over therebetween. The capacitor rapidlydischarges through this arc to produce a sharply rising current pulse.The inductance of the capacitor discharge circuit is held to a minimumvalue in order to maximize the rate of rise of this current pulse.

The turn-on switch 52 can be of any suitable conventional form. It isschematically shown as a normally nonconducting gap device having atrigger electrode 54 disposed between an anode and a cathode. When asufficient trigger voltage is applied between the trigger electrode andthe cathode of the gap device, the gap device becomes conducting, ineffect, closing.

For turning on the switch 2, any suitable control circuit can be used.In the illustrated embodiment, we have shown an overcurrent sensitivecontrol circuit 56. The circuit 56 comprises a current transformerhaving a secondary winding 57 magnetically coupled to the power line 9and a bridging rectifier 58 connected across the secondary winding 57.The output terminals of the bridging rectifier are connected across apotentiometer type resistor 59. The previously described triggerelectrode 54 is connected to a suitable tap on resistor 59 so that whenthe voltage across resistor 59 reaches a predetermined threshold value,sufficient voltage is present between the trigger electrode and thecathode of the gap device 52 to fire the gap device. Since the voltageacross resistor 59 is directly dependent upon the current in line 9, itwill be apparent that the gap device 52 will be fired in response to apredetermined current through line 9.

Another suitable control circuit is that shown in the aforementionedKotos application, where a tripping pulse is generated at a preselectedpoint on the current wave just prior to current zero. When such acircuit is used, this tripping pulse is applied to the trigger electrode54 to turn on the switch 52 and initiate opening.

OPERATING MECHANISM For transmitting opening force from the piston 28 tothe movable contact 15, we provide a bellcrank 60 which is pivotallymounted on a stationary pivot 62. One arm of the bellcrank is pivotallyjoined to the movable contact rod 20. The other arm of the bellcrank ispositioned to receive the rightward impact of piston 28. Thus, whenpiston 28 is driven to the right, it pivots bellcrank 60counterclockwise about its stationary pivot 62, thereby driving rod 20and movable contact l5 rapidly downward, thus opening the interrupter. Acompression spring 64, disposed between the bellcrank 60 and a portionof frame member 68, biases the contacts 15 and 16 together and tends tooppose contact-separating motion by piston 28. But the rapidly risingforce from piston 28 quickly overcomes the opposing bias of the spring64 to initiate operation.

Frame member 68 is pivotally mounted on stationary pivot 62, butnormally during the above-described operation of the electrohydraulicoperator, it remains stationary. For holding the frame stationary duringthis period, a releasable latch 70 is relied upon. A portion of thislatch is coupled to an actuating rod 72, which, in turn, is pivotallyconnected to the frame member 68, as by a suitable pin and slotconnection. So long as the latch is in its position of FIG. 1, theactuating rod 72 and the frame member 68 remain fixed When latch 70 isreleased (to initiate a resetting operation, as will soon be described)a spring 74 drives the rod 72 to the right, pivoting the frame member 68counterclockwise into its position of FIG. 3.

The force derived from the electrohydraulic operator, though it risesvery rapidly, if of a relatively short duration and can carry themovable contact at the desired high-speed through only a portion of itscomplete opening stroke. To complete the high-speed opening stroke, werely upon a mechanism which is slower in starting but can provide asustaining force that continues the opening operation after the forcepulse from the piston has lost its effectiveness. This latter mechanismcomprises an actuating lever pivotally mounted on a fulcrum 81 carriedby frame member 68. A compression spring 84 biases lever 80 in acounterclockwise direction about fulcrum 81 but is normally preventedfrom driving the lever 80 in this direction by the lower end ofbellcrank 60. But when bellcrank 60 is forced counterclockwise a shortdistance by motion of piston 28, the spring 84 drives actuating lever 80counterclockwise into its position of FIG. 2 against a stop 86 on framemember 68. In so moving, the actuating lever acts through a roller 87and cam 88 to force the bellcrank counterclockwise into its position ofFIG. 2. Roller 87 is carried on the actuating lever 80, and cam 88 isformed on the lower end of bellcrank 60. The length of the openingstroke can be increased by an appropriate change in the shape of cam 88.

The spring 84 and lever 80 may be thought of as constituting astored-energy followup operator. Cam 88 and roller 87 may be thought ofas releasable restraining means for holding the operator 84, 80 in itscharged condition. The lower arm of bellcrank 60 may be thought of asreleasing means for releasing the restraining means in response tooperation of the electrohydraulic operator 25.

An electrohydraulic operator similar to that illustrated hasdemonstrated that it can separate contacts by about thirteensixteentliinch in the extremely short time of 2 milliseconds. Only about 1.2milliseconds was required for a l-inch contact-separation. In thesetests, the mass of the movable contact structure was 0.4 pounds, and thearcing energy was obtained from a capacitor of 8.5 microfaradsprecharged to a voltage of l2 KV. Even higher speeds can be obtained byprecharging the capacitor to a higher level.

RESE'ITING OF THE OPERATING MECHANISM For resetting the actuating lever80 to its original position with respect to bellcrank 60 and framemember 68, the reset latch 70 is tripped to allow reset spring 74 todrive frame member 68 counterclockwise into the position of FIG. 3. Thiscounterclockwise motion of frame member 68 drives a tail 89 on theactuating lever 80 into engagement with a stationary stop 90.Thereafter, as frame member 68 continues moving counterclockwise, thisengagement of tail 89 with stop 90 causes actuating member 80 to pivotin a clockwise direction about its fulcrum 81, thus returning theactuating lever 80 to its original position with respect to thebellcrank 60 and frame member 68, as shown in FIG. 3. Such returnmovement of actuating lever 80 also recharges the opening spring 84.When actuating member 80 is moved through its resetting stroke into theposition of FIG. 3, it no longer holds bellcrank 60 in its operatedposition; but a stop 92 carried by frame member 68 engages bellcrank 60to continue holding the bellcrank in open position against the bias ofspring 64.

For releasing latch 70 to effect the above-described resetting action, atripping solenoid 100 is provided. This solenoid is connected in anoperating circuit 102 that includes a nonnally open switch 104. When themovable contact moves through a predetennined point in its openingstroke, the normally open switch 104 is closed to complete circuit 102,thereby operating the solenoid to trip latch 70 and initiate resetting.A mechanical linkage (not shown) between latch 70 and movable contactrod 20 could alternatively be used for releasing latch 70 in response toopening movement of contact rod 20.

ADDITIONAL MEANS FOR INITIATING AN OPENING OPERATION If it is desired toopen the circuit breaker at will or in response to conditions notrequiring extreme-high speed opening, the operating circuit 102 iscompleted by closing a switch 106, which may be manually operable orautomatically operable in response to preselected conditions. Switch 106is normally open but when closed completes an energizing circuit forsolenoid 100 to trip latch 70. Reset spring 74 responds to tripping oflatch 70 by driving frame member 68 counterclockwise from its positionof FIG. 1 into its position of FIG. 3, as explained hereinabove. The pin92 on frame member 68 engages bellcrank 60 to drive bellcrank 60counterclockwise about pivot 62 to open the interrupter. Theelectrohydraulic operator 25 remains inactive during such an openingoperation.

If an extra-high speed opening operation is desired, a manuallycontrolled switch 108 in parallel with gap device 52 can be operated todischarge capacitor 50 and cause the electrohydraulic operator toinitiate the opening operation. The opening operation thereaftercontinues in the same manner as described hereinabove.

CLOSING OF THE CIRCUIT BREAKER Closing of the circuit breaker iseffected by driving the reset rod 72 to the left from its position ofFIG. 3 into its position of FIG. 1. This causes frame member 68 to pivotclockwise about its stationary pivot 62; and such motion is transmittedto bellcrank 60 through spring 64, thus driving the bellcrankcounterclockwise about pivot 60 with the frame member 68. Thiscounterclockwise movement of bellcrank 60 drives movable contact rod 20upwardly to reengage contacts and 16.

The electrohydraulic operator 25 is reset to its position of FIG. 1prior to the initiation of a closing operation and is therefore inreadiness to reinitiate another opening operation as soon as thecontacts enter their engaged position should such opening be necessary,as a result, for example, of closing the circuit breaker on a faultedline. The electrohydraulic operator performs such an opening operationsimply by driving piston 28 to the right to pivot bellcrank 60counterclockwise to separate the contacts and release followup operator84 to complete the contact-separating operation. All of these openingoperations can be performed even though a leftward closing force is thenbeing applied to the actuating rod 72 inasmuch as the frame member 68may remain stationary while all these opening operations are takingplace. When the closing force is discontinued after such a close-openoperation, spring 74 will return reset rod 72 to its position of FIG. 3

to reset the mechanism.

While we have shown and described a particular embodiment of theinvention, it will be obvious to those skilled in the art that thevarious changes and modifications may be made without departing from ourinvention in its broader aspects; and we, therefore, intend herein tocover all such changes and modifications as fall within the true spiritand scope of our invention.

What I claim as new and desire to secure by Letters Patent of the UnitedStates is:

1. A high speed electric circuit breaker comprising:

a. a pair of separable contacts,

b. an electrohydraulic operator for producing extreme-high speedseparation of said contacts,

c. said electrohydraulic operator comprising a chamber containingliquid, means for developing an electric are within said liquid togenerate a shock wave in said liquid, a piston exposed to said liquidand movable at high-speed in response to said shock wave impactingagainst said piston,

d. linkage means mechanically connecting said piston to one of saidcontacts for imparting contact-separating force and motion from saidpiston to said one contact when said piston moves in response to receiptof said shock wave,

. said means for developing an are within said liquid comprising anormally charged capacitor, a pair of electrodes between which said arcis adapted to be formed, and means comprising a turn-on switch incircuit with said capacitor and said electrodes for initiating said areand for causing said capacitor to rapidly discharge therethrough,

f. only one are being initiated within said liquid per contactseparatingoperation,

g. a followup operator for continuing separation of said contacts aftersaid shock wave has begun contact-separating motion of said piston,

. restraining means for preventing said followup operator from operatingprior to operation of said electrohydraulic operator,

. and releasing means responsive to operation of said electrohydraulicoperator for releasing said restraining means to cause said followupoperator to continue separation of said contacts after saidelectrohydraulic operator has lost its initial effectiveness.

2. The circuit breaker of claim 1 in which: said restraining means andsaid releasing means comprise a cam member and a follower member, one ofwhich is coupled to said linkage and the other of which is coupled tosaid followup operator, said one member normally restraining saidfollowup operator from operating but moving in response to operation ofsaid electrohydraulic operator into a position wherein it is effectiveto restrain said followup operator from operating, said followupoperator acting thereafter through said cam and follower to impartcontact-opening motion to said linkage.

3. The circuit breaker of claim 1 in which:

a. said followup operator is a stored energy device,

b. said restraining means holds said stored energy device in a chargedcondition during initial operation of said electrohydraulic operator,

0. and said releasing means is coupled to said linkage means forreleasing said restraining means in response to operation of saidelectrohydraulic operator.

4. The circuit breaker of claim 1 in which:

a. said electrodes of the electrohydraulic operator are disposed insubstantially coaxial relationship and insulation is providedtherebetween,

b. said electrodes terminate in exposed portions between which said arcis initiated and which are located closely adjacent a wall of saidchamber.

5. The circuit breaker of claim 1 in which:

a. said electrodes have exposed metal portions between which said arc isformed, and

b. means is provided for directionally controlling the shock waveproduced by said are comprising a surface immediately adjacent saidexposed electrode portions which is a divergent surface of revolutionhaving an axis of revolution immediately adjacent which said exposedelectrode portions are located.

6. The circuit breaker of claim 1 in which said electrodes are spacedapart and insulated from each other prior to the formation of said aretherebetween.

7. A high-speed electric circuit breaker comprising:

a. a pair of separable contacts,

b. an electrohydraulic operator for producing extreme highspeedseparation of said contacts,

c. said electrohydraulic operator comprising a chamber containingliquid, means for developing an electric are within said liquid togenerate a shock wave in said liquid, a piston exposed to said liquidand movable at high-speed in response to said shock wave impactingagainst said piston,

d. linkage means mechanically connecting said piston to one of saidcontacts for imparting contact-separating force and motion from saidpiston to said one contact when said piston moves in response to receiptof said shock wave,

e. said means for developing an arc within said liquid comprising anormally charged capacitor, a pair of electrodes between which said arcis adapted to be formed, and means comprising a turn-on switch incircuit with said capacitor and said electrodes for initiating said areand for causing said capacitor to rapidly discharge therethrough,

a followup operator for continuing separation of said contacts aftersaid shock wave has begun contact-separating motion of said piston,

g. restraining means for preventing said followup operator fromoperating prior to operation of said electrohydraulic operator,

h. releasing means responsive to operation of said electrohydraulicoperator for releasing said restraining means to cause said followupoperator to continue separation of said contacts after saidelectrohydraulic operator has lost its initial effectiveness,

i. said followup operator being a stored energy device,

j. said restraining means holding said stored energy device in a chargedcondition during initial operation of said electrohydraulic operator,

k. said releasing means being coupled to said linkage means forreleasing said restraining means in response to operation of saidelectrohydraulic operator,

1. and reset means provided for recharging said stored-energy followupoperator and restoring said restraining means to a reset condition forholding said stored energy followup operator charged,

m. said reset means comprising a stored-energy reset operator, meansresponsive to a condition which initiates circuit breaker opening forcausing said reset operator to discharge and supply energy forresetting, and means operated by said reset operator for recharging saidstored-energy followup device and restoring said restraining means tosaid reset condition.

A high-speed electric circuit breaker comprising:

a. a pair of separable contacts,

b. an electrohydraulic operator for producing extreme-high speedseparation of said contacts,

c. said electrohydraulic operator comprising a chamber containingliquid, means for developing an electric arc within said liquid togenerate a shock wave in said liquid a piston exposed to said liquid andmovable at high-speed in response to said shock wave impacting againstsaid piston,

d. linkage means mechanically connecting said piston to one of saidcontacts for imparting contact-separating force and motion from saidpiston to said one co'ntact when said piston moves in response toreceipt of said shock wave,

e. said means for developing an are within said liquid comprising anormally charged capacitor, a pair of electrodes between which said arcis adapted to be formed, and means comprising a turn-o n switch incircuit with said capacitor and said electrodes for initiating said arcand for causing said capacitor to rapidly discharge therethrough,

. followup operating means for continuing separation of said contactsafter said shock wave has begun contactseparating motion of said piston,and

g. reset means operable in response to a condition which initiatescircuit breaker opening for resetting said followup operating means to astate of preparedness for another operation following a first operationby said followup operating means.

1. A high speed electric circuit breaker comprising: a. a pair ofseparable contacts, b. an electrohydraulic operator for producingextreme-high speed separation of said contacts, c. said electrohydraulicoperator comprising a chamber containing liquid, means for developing anelectric arc within said liquid to generate a shock wave in said liquid,a piston exposed to said liquid and movable at high-speed in response tosaid shock wave impacting against said piston, d. linkage meansmechanically connecting said piston to one of said contacts forimparting contact-separating force and motion from said piston to saidone contact when said piston moves in response to receipt of said shockwave, e. said means for developing an arc within said liquid comprisinga normally charged capacitor, a pair of electrodes between which saidarc is adapted to be formed, and means comprising a turn-on switch incircuit with said capacitor and said electrodes for initiating said arcand for causing said capacitor to rapidly discharge therethrough, f.only one arc being initiated within said liquid per contactseparatingoperation, g. a followup operator for continuing separation of saidcontacts after said shock wave has begun contact-separating motion ofsaid piston, h. restraining means for preventing said followup operatorfrom operating prior to operation of said electrohydraulic operator, i.and releasing means responsive to operation of said electrohydraulicoperator for releasing said restraining means to cause said followupoperator to continue separation of said contacts after saidelectrohydraulic operator has lost its initial effectiVeness.
 2. Thecircuit breaker of claim 1 in which: said restraining means and saidreleasing means comprise a cam member and a follower member, one ofwhich is coupled to said linkage and the other of which is coupled tosaid followup operator, said one member normally restraining saidfollowup operator from operating but moving in response to operation ofsaid electrohydraulic operator into a position wherein it is effectiveto restrain said followup operator from operating, said followupoperator acting thereafter through said cam and follower to impartcontact-opening motion to said linkage.
 3. The circuit breaker of claim1 in which: a. said followup operator is a stored energy device, b. saidrestraining means holds said stored energy device in a charged conditionduring initial operation of said electrohydraulic operator, c. and saidreleasing means is coupled to said linkage means for releasing saidrestraining means in response to operation of said electrohydraulicoperator.
 4. The circuit breaker of claim 1 in which: a. said electrodesof the electrohydraulic operator are disposed in substantially coaxialrelationship and insulation is provided therebetween, b. said electrodesterminate in exposed portions between which said arc is initiated andwhich are located closely adjacent a wall of said chamber.
 5. Thecircuit breaker of claim 1 in which: a. said electrodes have exposedmetal portions between which said arc is formed, and b. means isprovided for directionally controlling the shock wave produced by saidarc comprising a surface immediately adjacent said exposed electrodeportions which is a divergent surface of revolution having an axis ofrevolution immediately adjacent which said exposed electrode portionsare located.
 6. The circuit breaker of claim 1 in which said electrodesare spaced apart and insulated from each other prior to the formation ofsaid arc therebetween.
 7. A high-speed electric circuit breakercomprising: a. a pair of separable contacts, b. an electrohydraulicoperator for producing extreme high-speed separation of said contacts,c. said electrohydraulic operator comprising a chamber containingliquid, means for developing an electric arc within said liquid togenerate a shock wave in said liquid, a piston exposed to said liquidand movable at high-speed in response to said shock wave impactingagainst said piston, d. linkage means mechanically connecting saidpiston to one of said contacts for imparting contact-separating forceand motion from said piston to said one contact when said piston movesin response to receipt of said shock wave, e. said means for developingan arc within said liquid comprising a normally charged capacitor, apair of electrodes between which said arc is adapted to be formed, andmeans comprising a turn-on switch in circuit with said capacitor andsaid electrodes for initiating said arc and for causing said capacitorto rapidly discharge therethrough, f. a followup operator for continuingseparation of said contacts after said shock wave has beguncontact-separating motion of said piston, g. restraining means forpreventing said followup operator from operating prior to operation ofsaid electrohydraulic operator, h. releasing means responsive tooperation of said electrohydraulic operator for releasing saidrestraining means to cause said followup operator to continue separationof said contacts after said electrohydraulic operator has lost itsinitial effectiveness, i. said followup operator being a stored energydevice, j. said restraining means holding said stored energy device in acharged condition during initial operation of said electrohydraulicoperator, k. said releasing means being coupled to said linkage meansfor releasing said restraining means in response to operation of saidelectrohydraulic operator, l. and reset means provided for rechargingsaid stored-energy followup operatOr and restoring said restrainingmeans to a reset condition for holding said stored energy followupoperator charged, m. said reset means comprising a stored-energy resetoperator, means responsive to a condition which initiates circuitbreaker opening for causing said reset operator to discharge and supplyenergy for resetting, and means operated by said reset operator forrecharging said stored-energy followup device and restoring saidrestraining means to said reset condition.
 8. A high-speed electriccircuit breaker comprising: a. a pair of separable contacts, b. anelectrohydraulic operator for producing extreme-high speed separation ofsaid contacts, c. said electrohydraulic operator comprising a chambercontaining liquid, means for developing an electric arc within saidliquid to generate a shock wave in said liquid, a piston exposed to saidliquid and movable at high-speed in response to said shock waveimpacting against said piston, d. linkage means mechanically connectingsaid piston to one of said contacts for imparting contact-separatingforce and motion from said piston to said one contact when said pistonmoves in response to receipt of said shock wave, e. said means fordeveloping an arc within said liquid comprising a normally chargedcapacitor, a pair of electrodes between which said arc is adapted to beformed, and means comprising a turn-on switch in circuit with saidcapacitor and said electrodes for initiating said arc and for causingsaid capacitor to rapidly discharge therethrough, f. followup operatingmeans for continuing separation of said contacts after said shock wavehas begun contact-separating motion of said piston, and g. reset meansoperable in response to a condition which initiates circuit breakeropening for resetting said followup operating means to a state ofpreparedness for another operation following a first operation by saidfollowup operating means.